THE STRUGGLE FOR LIBERTY 123 



circles, with which he sometimes amused his leisure, 

 as a sort of ingenious trifling. At the very time 

 that the question of the propagation of storms arose 

 in his mind he had contrived the Pennsylvania fire- 

 place, which was to achieve cheap, adequate, and 

 uniform heating for American homes. His aspira- 

 tion was for a free people, well sheltered, well fed, 

 well clad, well instructed. 



In 1747 Franklin made what is generally consid- 

 ered his chief contribution to science. One of his 

 correspondents, Collinson (a Fellow of the Royal 

 Society and a botanist interested in useful plants, 

 through whom the vine was introduced into Vir- 

 ginia), had sent to the Library Company at Phila- 

 delphia one of the recently invented Leyden jars 

 with instructions for its use. Franklin, who had 

 already seen similar apparatus at Boston, and his 

 friends, set to work experimenting. For months he 

 had leisure for nothing else. In this sort of activity 

 he had a spontaneous and irrepressible delight. By 

 March, 1747, they felt that they had made discov- 

 eries, and in July, and subsequently, Franklin re- 

 ported results to Collinson. He had observed that a 

 pointed rod brought near the jar was much more 

 efficacious than a blunt rod in drawing off the 

 charge ; also that if a pointed rod were attached to 

 the jar, the charge would be thrown off, and accu- 

 mulation of charge prevented. Franklin, moreover, 

 found that the nature of the charges on the inside 

 and on the outside of the glass was different. He 

 spoke of one as plus and the other as minus. Again, 

 " We say B (and bodies like-circumstanced) is 

 electricized positively; A negatively." Dufay had 



